Air cellular cushioning articles suitable for packaging applications have been in commercial use for several decades. One of the products in widespread use is BubbleWrap® cellular cushioning, one embodiment of which is made by using heat and vacuum to form spaced-apart, air-filled cavities in a first film and thereafter heat sealing a flat second “backing” film to the flats between the cavities of the first film, so that air is entrapped in the formed cavities making up the individualized cells. The resulting air-cellular cushioning product comprises discrete closed bubbles. If any one bubble bursts, no other bubble necessarily deflates. One significant disadvantage of BubbleWrap® cellular cushioning product is that shipping costs are high per unit weight of product because the product density is low, i.e., the shipping of such products is mostly shipping air.
Bubble Wrap® cellular cushioning has been made from multilayer films having outer seal layers, a central gas barrier layer, and a tie layer between each of the seal layers and the barrier layer. The tie layer has been made from an anhydride modified low density polyethylene, with an anhydride content of about 141 parts per million, based on the weight of the anhydride modified low density polyethylene in the tie layer.
Although Bubble Wrap® cushioning products have not been displaced by inflatable flexible cushioning articles, in the past there have been a number of commercialized air-cellular cushioning products for packaging which have been designed to be inflated by the end user, i.e., inflated and sealed shut immediately before end use by the packager. These products offer the advantage of being shippable before inflation, providing for much more efficient transport and storage before use, as any given volume within a truck or warehouse can hold over thirty times as much product if it is uninflated rather than shipped to the packager while inflated. One of these products has been made from the same multilayer film used for Bubble Wrap® cellular cushioning.
These “inflatable” cellular packaging products differ from BubbleWrap® cellular cushioning in a number of ways. One notable difference between inflatable cushioning products and BubbleWrap® cellular cushioning is that the inflatable cushioning articles have a plurality of chambers extending from a fill zone, with each of the chambers containing a series of interconnected inflatable bubbles (i.e., “cells”), with each series of bubbles extending transversely across the web. Air within one of the cells of a particular series can freely move within other cells of the same series. More particularly, if a load is placed on one of the bubbles in the series, the bubble can partially or fully collapse as air is displaced from within the bubble, with the air moving to the other bubbles in the series. The displacement of air from one bubble to others can be detrimental to a packaged product because the product may no longer be receiving adequate cushioning protection. It would be desirable to reduce or eliminate this “bottoming out” tendency in an inflatable air cellular product.